The integrated circuit package is the building block used in a high performance electronic system to provide applications for usage in products such as robotics equipment, gps devices, advanced cell phone devices, medical electronic devices, and a vast line of other similar products that require small compact electronics supporting many complex functions.
The traditional integrated circuit package typically consists of a package base or package substrate providing a mounting structure for attachment of at least one chip or die and an enclosure such as an epoxy applied on it to protect its contents. Typically, one side of the chip or the die is used primarily for the mounting the chip or die. The other side of the chip or the die, referred to as an active surface of the chip or the die, has electrically conductive areas that provide for electrical connections to its circuitry.
High performance compact devices requiring small dimensions of length, width, and thickness are highly sought after in the competitive world markets. Design and development of the chip or the die having small length, width, and thickness as well as high performance functionality and reliability are increasingly growing in demand. A sought after package solution prevalent to meeting these requirements and offering additional benefits is called a flip chip.
The flip chip consists of the chip or the die having its active surface connected onto a substrate using connectors consisting of electrically conductive material. The side opposite the active surface of the flip chip is without protection such as an enclosure or epoxy and thus its surface is exposed. The flip chip, not having an enclosure, provides a lower height than the traditional integrated circuit packages resulting in the extremely thinner devices.
The flip chip provides improvements in manufacturing and reliability over the traditional integrated circuit packages due to the fewer assembly steps and processes such as connections, wire routing, packaging lead placement, package lead formation, and error prone handling during assembly. Circuitry of the flip chip can be optimized for performance due to the shorter distances between the circuitry and the substrate over traditional integrated circuit packages.
Since the flip chip is not enclosed, it is crucial to prevent possible problems due to heat. Heat generated by the flip chip can cause temporary or permanent failure of the circuitry within the flip chip. Heat generated by the flip chip can cause mechanical failure such as loss of connections to the substrate. Heat generated by the flip chip can cause structural failure such as cracking or warping of the chip or the die.
A key to solving heat related issues of the flip chip is the application of a compound material such as a thermally conductive epoxy to the areas subjected to the most heat related stress. The compound material is applied between the active surface of the flip chip and the substrate. The compound fills gaps between and around the connectors and fills areas between the flip chip and the substrate. The compound material is often cured, effectively cementing the flip chip, the connectors between the flip chip, and the substrate together as a single integrated circuit package.
The compound material can only be effective if sufficient amounts can be applied into the gap areas between the flip chip and the substrate. The gap height or gap distance is the distance between the active surface of the flip chip and the substrate surface connected to the flip chip. The larger the gap height, the more compound material can be applied into the gap areas resulting in improved avoidance of heat related problems.
Typical industry solutions to increase gap height involve the use of larger connectors to raise the flip chip higher away from the substrate. This compromises key objectives and advantages, such as cost, simplicity, and height dimensions of the resulting integrated circuit package. Other alternative solutions to increase the gap height involve specially designed substrates involving complex fabrication processing, costs, or substrates resulting in structural integrity related issues.
Attempts have failed to provide a complete solution addressing high performance compact integrated circuit packages having small thin profiles, high reliability, low cost and simplified manufacturing processing.
In view of the ever-increasing commercial competitive pressures, along with growing consumer expectations and the diminishing opportunities for meaningful product differentiation in the marketplace, it is critical that answers be found for these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.